396 Mr. Greatorex’s observations on the heights 
The graduation commenced from a zero about 3 feet from 
the bottom of the staff, so that from the zero to its top was 
exactly 25 feet ; the top ending in a bluntish point. 
Twelve feet six inches of the upper part of the staff could 
occasionally be separated from the lower part, both for the 
convenience of carrying, and in case the wind should prevent 
the use of the whole length. Small cords were also attached 
to it, for the purpose of holding it steady and perpen- 
dicular. 
We first determined the height of Otley’s house above 
the lake, which was 10 yards, and at this height the 
stationary barometer was placed ; and Mr. Crosthwaite, of 
the Keswick Museum, undertook to note its variation and that 
of the thermometer every half hour. 
We then ascended Skiddaw, accompanied by Mr. Airey, a 
black-lead pencil maker (who proved an excellent assistant), 
and two boys. On the summit the barometer was set up. I 
first adjusted it, and privately noted down the height of the 
mercury ; then purposely deranged it, to let Otley re-adjust 
it, and write down his observation, which never differed from 
mine more than one thousandth of an inch during the whole 
series of observations. The heights of the attached and 
detached thermometers being also noted, we proceeded to the 
measurement by the level and staff. 
The telescope being levelled, and its cross wires intersect- 
ing the highest point of the mountain, it was then pointed in 
the direction of the most convenient descent, and the staff 
carried down the hill till its top exactly coincided with the 
cross wires, the level of the telescope being carefully pre- 
served ; the perpendicularity of the staff was ascertained by 
